Chain saw



FIG. 1 is a right side elevational view of a chain saw showing my new design;

FIG. 2 is a left side elevational view thereof;

FIG. 3 is a back side elevational view thereof;

FIG. 4 is front side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a perspective view thereof.

The broken lines in the drawings illustrate portions of the chain saw which form no part of the claimed design. 

CLAIM What is claimed is the ornamental design for a chain saw, as shown and described. 